1. Field of the Invention
This invention generally relates to data transmission systems which use intermediate buffer memories to transmit data from recording media. Particularly, this invention relates to the data transmission systems provided for prevention of unauthorized copy of the data of the recording media which are captured from stored contents of the intermediate buffer memories.
This application is based on Patent Application No. Hei 10-127907 filed in Japan, the content of which is incorporated herein by reference.
2. Description of the Related Art
There are provided a variety of methods and apparatuses for prevention of digital copying of data, as follows:
The paper of Japanese Patent Application, Publication No. Hei 6-105032 discloses an example of an image forming device managing system, wherein download of image data to a copying machine is temporarily stopped until completion of copying while received image data are temporarily stored in a buffer memory so that they are transferred to a main memory after completion in reception of the image data. Thus, it is possible to perform download of the data to the copying machine with a short period of time in communications, while it is possible to prevent abnormal copying which occur when a copy is started before transfer of the image data is completed.
The paper of Japanese Patent Application, Publication No. Hei 8-237596 discloses an example of a method and apparatus for copy prevention in a digital magnetic recording/reproduction system, wherein a copy authorization is detected using a marker which is formed by a control word for scrambling audio and video bit streams and copy protection (CP) information used for prevention of unauthorized copy and which is subjected to encryption using a cipher key and is recorded on a video tape, for example. Herein, the control word is reproduced from the marker and is subjected to descrambler to enable display on a monitor.
Conventionally, some of the data transmission systems or data communication systems normally use intermediate buffer memories to transmit data from one location to another. However, such data transmission system is not always capable of processing all data streams stored in the intermediate buffer memory at a time. Particularly, in the case of the software processing, the system captures a limited amount of data, which can be processed at one time, among all of the data accumulated in the intermediate buffer memory. So, the system processes limited amounts of data successively.
FIG. 6 is a block diagram showing an example of the conventional data transmission system in which data stream processing is performed by means of an intermediate buffer memory.
In FIG. 6, data streams are read from a recording medium (or recording media) 1 and are temporarily stored in a stream buffer 2 to an extent that they will not overflow. Then, a stream processing unit 3 accesses the stream buffer 2 to capture an amount of the data stream(s), which can be processed at one time. So, the stream processing unit 3 processes amounts of the data streams successively.
Thereafter, processing results of the data streams are output to an output unit 4, which in turn provides corresponding outputs to the external device or system (not shown).
In the aforementioned system, it is possible to easily capture the stored content of the intermediate buffer memory (i.e., stream buffer 2) by the known techniques such as the memory snapshot. So, it is possible to make a duplication with ease. However, this raises a problem in protection of the copy right. So, it is strongly demanded to provide a solution in the protection of the copy right with respect to the data transmission system which uses the intermediate buffer memory for transmission (or communication) of data from the recording medium.